Sensitivity Evaluation of AP1000 Nuclear Power Plant Best Estimation Model

The best estimation process of AP1000 Nuclear Power Plant (NPP) requires proper selections of parameters and models so as to obtain the most accurate results compared with the actual design parameters. Therefore, it is necessary to identify and evaluate the influences of these parameters and modeling approaches quantitatively and qualitatively. Based on the best estimate thermal-hydraulic system code RELAP5/MOD3.2, sensitivity analysis has been performed on core partition methods, parameters, and model selections in AP1000 Nuclear Power Plant, like the core channel number, pressurizer node number, feedwater temperature, and so forth. The results show that core channel number, core channel node number, and the pressurizer node number have apparent influences on the coolant temperature variation and pressure drop through the reactor. The feedwater temperature is a sensitive factor to the Steam Generator (SG) outlet temperature and the Steam Generator outlet pressure. In addition, the cross-flow model nearly has no effects on the coolant temperature variation and pressure drop in the reactor, in both the steady state and the loss of power transient. Furthermore, some fittest parameters with which the most accurate results could be obtained have been put forward for the nuclear system simulation

Resolved shear stress intensity coefficient and fatigue crack growth in large crystals

Fatigue crack growth in large grain Al alloy was studied. Fatigue crack growth is caused primarily by shear decohesion due to dislocation motion in the crack tip region. The crack paths in the large crystals are very irregular and zigzag. The crack planes are often inclined to the loading axis both in the inplane direction and the thickness direction. The stress intensity factors of such inclined cracks are approximated from the two dimensional finite element calculations. The plastic deformation in a large crystal is highly anisotropic, and dislocation motion in such crystals are driven by the resolved shear stress. The resolved shear stress intensity coefficient in a crack solid, RSSIC, is defined, and the coefficients for the slip systems at a crack tip are evaluated from the calculated stress intensity factors. The orientations of the crack planes are closely related to the slip planes with the high RSSIC values. If a single slip system has a much higher RSSIC than all the others, the crack will follow the slip plane, and the slip plane becomes the crack plane. If two or more slip systems have a high RSSIC, the crack plane is the result of the decohesion processes on these active slip planes

Rotating and twisting charged black holes with cloud of strings and quintessence as a particle accelerator

In this paper, we study the effects of the rotation parameter $a$, the twist parameter $n$, the string cloud parameter $b$, the quintessence state parameter $\omega _{q}$ and the charge parameter $q$ on the horizons and ergosphere of rotating and twisting charged black holes with cloud of strings and quintessence, and obtain the equations of motion and effective potential of the particle on the equatorial plane of black hole. We find that a particle with the critical angular momentum $L = L_C$ falling from infinity reaches the event horizon($u^r$=0) and satisfies the circular orbit condition $V_{e f f}={V_{e f f}}'=0$. We derive the expression of the centre-of-mass (CM) energy of two particles with different masses from the equations of particle motion. We show that the CM energy can be arbitrarily large for extremal black holes when the particles reach the event horizon by adjusting the angular momentum of the incident particles. However, for non-extremal black holes, the CM energy of particles that reach the event horizon cannot diverge by adjusting the angular momentum of the incident particles.Comment: 17 pages, 7 figures, 2 Table